Soumya Mukherjee

In situ Preparation of SiO2-WC Nanocomposites through Sol-Gel Route

SiO2-WC nanocomposites have been prepared by in situ reduction of (NH4)2WO4 with dextrose in the SiO2 gel matrix by heating within the temperature range of 1250°-1300°C for half an hour in nitrogen atmosphere. The average particle size of WC formed is about 24 nm.

Synthesis and Characterization of CNT Reinforced Alumina based Nanocomposite

Carbon nanotube (CNT) reinforced alumina matrix nanocomposite was successfully synthesized by two different techniques. In the first process sol-gel method was used to generate 3 wt% homogeneously distributed CNT in alumina matrix after sintering. In another novel method chemical mixing process was adopted for synthesis of CNT-alumina nanocomposite powder to generate maximum of 10 wt% CNTs in the alumina matrix after sintering. Phase identification was done by XRD and the particle size was measured by Scherrer and Williamson-Hall plot. Compared to pure alumina the hardness of the nanocomposite was improved by 3–18% for different wt% of CNTs. The hardness of the nanocomposite enhanced due to an enhanced load carrying capacity of homogeneously distributed CNTs.

Effect of Zn Doping on the Crystallization, Dielectric, and Ferroelectric Properties of Solid State Sintered Barium Stannate

Perovskite-type crystalline undoped and zinc doped (10, 15, 20, and 25 mole-% concentration) BaSnO3 were prepared based on modified solid state process with agate mill activation. An annealing temperature of 1473 K was selected from a DSC-TGA study for the preparation of undoped and zinc doped BaSnO3. Phase evolutions of the sintered samples were done by XRD studies. Morphological features were studied by FESEM and the presence of elements was identified by EDX to confirm the compositions of the material. Raman active modes and M-O coordinations were obtained from Raman spectra; FTIR analyses confirming the successful synthesis of undoped and doped perovskite. Optical properties were confirmed by UV-VlS and PL spectra analyses. The band gap was estimated to increase with dopant concentrations. PL emission was observed to be in the visible spectrum for doped samples. It was found that with an increase in Zn doping concentrations on BaSnO3 there was a decrease in the ferroelectricity. The decrease in ferroelectric behavior may be due to an increase of defect induced conductivity at lattice sites with an increase of Zn doping.

Effect of CNT Additions on a Magnesia-based Refractory in Relation to Morphology and Oxidation Behaviour

The performance of a MgO-based refractory is studied after addition of carbon nanotubes (CNT) into the matrix with the presence of graphite. The dispersion is done with sonications in alcohol along with optimum addition of required material. X-ray diffraction (XRD) analysis executes identification of proper phase. From Fourier transform infrared spectroscopy (FTIR) studies, no distinct changes are observed in spectral analysis between two mixed samples after addition of CNT on the matrix. Field emission scanning electron microscopy (FESEM) studies elicidate morphology of the sample prepared. It also indicates that dispersion of CNT is possible only after functionalization to nave a COOH group with aqua regia (HNO3: H2SO4 = 3 : 1). CNT dispersion is not satisfactory under ultrasonication in ethanol media even after 15 h and 20 h of operation. CNT remain entangled by a certain portion within the matrix of the material. Thermal behaviour based on thermogravimetric analysis (TGA) is carried with and without CNT addition in the MgO-C matrix to correlate oxidation behaviour of the MgO-C-CNT.

Phase Evaluation of Pure Nanocrystalline Barium Stannate by Two Different Milling Activations

Pure nanocrystalline BaSnO3 is prepared by two methods: mechanical activation (planetary ball milling) and mechanical hand mixing in agate mortar followed by sintering for both at 1350°C/ 2 h. The phase formations during synthesis are analyzed by x-ray diffraction (XRD) studies and the crystallite size is measured by Scherrer’s formula from the major peaks of the diffractogram. The nanocrystalline barium stannate having single phase simple cubic perovskite structure is synthesized with a crystallite size about 50 nm. Fourier transform infrared spectroscopy (FTIR) is done to determine symmetric and asymmetric stretching of the bonds formed and co-ordination of the ions within crystal structure. FTIR studies justify the phases developed by XRD since the molecular signature and co-ordination of cations are verified. Microstructure and morphology are observed by scanning electron microscopy (SEM), while energy dispersive x-ray analysis (EDX) is done to determine the presence of the required element of composition formation. Ultra violet-visible spectroscopy (UV-VIS) shows absorption spectra of the sample within the UV region, while the band gap is calculated using the Tauc relation. The band gap evaluated for nanocrystalline barium stannate is about 2–2.78 eV for indirect transition, while for direct transition it is about 2.78–3.14 eV. The value is observed to be close to that of semiconductor-based materials.

Synthesis, Characterization and Bandgap Evaluation of Bismuth Ferrite-Zinc Ferrite Nanocomposites prepared by Chemical Route

Chemical route was selected for synthesis of the nanocomposite material of perovskite bismuth ferriteinverse spinel zinc ferrite. Heat treatment for proper phase development was carried out at 500°C for 2, 3 and 4 h respectively. Crystalline peaks were identified from XRD analysis for both perovskite and inverse spinel phase. The crystallite size was calculated by Scherrers formula. The extent of formation of perovskite was found to be more than that of spinel phase. Microstructures were obtained from FESEM (field emission electron microscope) analysis, which exhibited agglomeration tendency and granular particle shape. FTIR analysis was carried out to find out the molecular signature of the sample. HRTEM image was analyzed to obtain the d-values of the nanocomposite, which was found to be in line with the results of XRD phase identification, thus confirming successful synthesis. UV-Vis analysis was studied in the range of 200-700 cm in transmission mode. Using Tauc relation, αhν = B(hν-Eg)2, bandgap of heat treated samples at 500°C for 2, 3 and 4 h were evaluated to be around 2.93 eV. From bandgap calculation, it was concluded that the material might be suitable for photocatalytic application in visible range, opto-electronic devices having switching domain in visible range.

A Comprehensive Review of Recent Advances in Magnesia Carbon Refractories

The paper describes state of the art developments in the formulation of MgO-C refractories, products that have been an integral part of the iron and steel industry over the last two decades. The effects of important techniques and variations in operational parameters are reviewed and summarized, including the impact of antioxidants on oxidation behaviour, incorporation of graphite or nano carbon content, and the influence of electromagnetic fields on slag corrosion resistance. Most of the major experimental findings related to properties of MgO-C refractories are a focus of the article. It addresses the oxidation kinetics of magnesia carbon refractory bricks, the microstructure of graphite and nano carbon-containing MgO-C refractories, determination of the mineralogical composition of MgO-C refractories by the Rietvelt method, and the mechanical behaviour of these refractories.